1. Field of the Invention
The present invention particularly relates to a data recording device, data recording method, and recording control program for recording data in compliance with Digital Versatile Disc (DVD)-Video specifications.
2. Description of Related Art
DVD is the next standard of high-capacity optical discs to replace Compact Disc (CD). Video data and audio data are recorded on DVD (DVD-R, DVD-RW, DVD-RAM, and so on) as a recording medium. The recorded data is compressed and encoded in accordance with the DVD-Video specifications, for example.
Referring first to FIG. 10, a DVD recording device 101 as a data recording device has a system controller 102, encoder 103, stream buffer memory 104, and disc unit 106. The system controller 102 controls the operation of each component of the DVD recording device 101. The encoder 103 compresses and encodes video data and audio data using Moving Picture Expert Group (MPEG)-2 technology. The stream buffer memory 104 is used to supplement the contents of Navigation pack, which is referred to hereinafter as “NV_PCK”, such as playback control information contained in a data stream generated in the encoder 103. The disc unit 106 has an optical head to write data onto a recording medium 105 composed of DVD.
A data stream consists of a series of cells. Each cell includes a plurality of Video Object Units (VOBUs). The NV_PCK is placed at the beginning of each VOBU and composed of data for controlling playback of video data and audio data, and data for providing support for special playback modes such as skip playback, as described in Japanese Unexamined Patent Application Publications 2002-56609 and 10-134548, for example. In the DVD-VIDEO specifications, the maximum number of cells is limited to 255.
The encoder 103 compresses and encodes video data and audio data to generate a data stream. The number of VOBUs in one cell is a fixed value corresponding to a recording time.
The encoder 103 performs the compression encoding using a variable bit rate control method. The variable bit rate control method varies a video bit rate, which is an amount of data per unit time, according to a variation in video data.
A minimum capacity of the stream buffer memory 104 is the size of one cell. A maximum size of one cell is determined based on the maximum size of VOBU (maximum code amount) and the number of VOBUs in one cell. The number of VOBUs in one cell is fixed.
Thus, a capacity Q[Mb] of the stream buffer memory 104 is given by the following equation (1):Q=(RV+RA)(N/RF)V  (1)where RV is a maximum video bit rate [Mbps], RA is an audio bit rate [Mbps] as an amount of audio data per unit time, N is the number (N) of video frames or the number of still frames included in one VOBU, RF is a video frame rate [Hz] or a still frame rewriting frequency, and V is the number of VOBUs in one cell. The maximum video bit rate RV is set to a given value in order to keep a constant image quality.
In this way, the capacity Q of the stream buffer memory 104 is determined according to the maximum video bit rate that varies by the variable bit rate control performed by the encoder 103. Use of the sufficiently large capacity Q allows all the data in one cell to be always stored in the stream buffer memory 104.
If, on the other hand, the capacity Q of the stream buffer memory 104 is predetermined, the fixed value of the number of VOBUs in one cell is adjusted. This adjustment allows all the data in one cell to be always stored in the stream buffer memory 104.
A maximum recording time tmax is given by the following equation (2):tmax=CV(N/RF)  (2)where C is the number of cells, which is C=255. Thus, the maximum recording time tmax varies with the number of VOBUs, V, in one cell.